Electric heating device



March 19, 1929; RAF 1,706,385

ELECTRIC HEATING DEVICE Filed Jan. '7, 1928 Patented Mar. 19, 1929.

UNITED STATES PATENT OFFICE.

CARL GRAI, OF MANNHEIM, GERMANY, ASSIGNOR OF ONE-HALF T0 KARL REICHL, OF PHILADELPHIA, PENNSYLVANIA.

ELECTRIC HEATING DEVICE.

Application filed January 7, 1928, Serial No. 245,157, and in Germany February 11, 1927.

My invention relates to electric heating devices for warming parts of the human body. Prior to my present invention, devices have been made for the above mentioned purpose, which however, were unsatisfactory and dangerous due to the unstable arrangement of the heating elements which impaired and caused-the destruction of the insulating parts. Other disadvantages of said prior devices, especially when used as foot warmers, were their inability to properly flex and provide sufficient elasticity to accommodate the natural foot movements without destroying the stable arrangement of the parts of the devices and causing short circuits, burning of the parts and injury to the wearer.

A still further disadvantage of said prior devices, is that they are liable to absorb perspiration to such extent that the insulating substance will become conductive and subject parts of the human body to the electric current applied to the heating ele-.

ment.

' One object of my invention is to provide heating devices for said purpose but in which said disadvantageous conditions of said prior devices are eliminated and to so make my improved devices that they can be used with freedom, comfort and safety.

Another object is to so make my improved devices that they will be durable and will take up a comparatively small amount of space.

These objects and other advantageous ends attain in the following manner, reference bein had to the accompanying drawing in whici Figure l. is a plan view of an electrically heated insole made in accordance with my present invention,

Figure 2 is a longitudinal view of said insole,

Figure 3 is an enlarged plan view, partly opened and in section, showing the construction of said insole,

Figure 4 is a com lete outside plan view of said insole inclu ing the edge. binding,

Figure 5 is an edge view of Figure 4, and

Figure 6 is an enlarged sectional view taken on the line 6-6 of Figure 3; for the sake of clearness in reading the drawing, the proportion of the width and thickness is exaggerated.

In carrying out my invention, the heating element is hermetically enclosed in a water-proof and water indissoluble substance, the whole structure making up a flexible elastic yet stable system.

Referring specifically to the drawings, an elongated strip of strong insulating paper, such for example as red rope paper about 0.009 inches thick is folded to produce a flattened tube 7. About this flattened tube is wound or coiled a double cotton-covered thin electric resistance wire 8, whose thickness can vary within the range of 0.002 inches and 0.004 inches in diameter depending on the predetermined standard voltage, 110 to 220 volts. For special cases however, by using a larger size of wire, the devices can be designed for an electric source less than 110 volts.

One end of the resistance wire 8 is soldered at 9 to an insulated copper Wire 10 on the outside of the tube 7. This copper wire 10 then extends into the tube 7 through a hole 11 in said tube. After passing through the interior of the tube 7, the copper wire 10 is laced outwardly and inwardly through the respective holes 12 and 13 in the tube 7, and the wire 10 is soldered at 14 to the current supply lead 15 within the confines of the tube 7. The other end of the resistance wire 8 is soldered at 16 to another insulated cop'- per wife 17. The Wire 17 extends through a hole 18 in the tube 7 into the tube where it passes lengthwise through the interior and is laced outwardly and inwardly through the respective holes 19 and 20 in the tube and said copper wire 17 is soldered at 21 to the other current supply lead 22 within the confines of the tube 7. v

The windings of the coil of wire 8 are covered and enclosed by a water-proof and high dielectric envelope 23 of impregnated cloth such for example as varnish cambric 0.007 inches thick. This envelope is pasted or glued in position to cover the convolutions of the wire coil 8. The pasting of the en'- velope is preferably done with glue or sticker so that .the entire heating element is enclosed by the envelope. The rear end of the tube and the wire leads are entirely enclosed in an envelope 24 of linen which is overlapped, pasted and coated by a water-proof solution such for example as a mixture of one part of collodium wool and three parts of a zeton.

Finally the heating element thus enveloped nected in series with a suitable supply of electricity. The devices can be pla within slippers or shoes, sufiicient flexibility being present to allow freedom of movement and comfort to the wearer. heating element being hermetically sealed within water-proof material, moisture can not reach the heating element and short circuit will thus be prevented.

In addition, the arrangement of the heating coil on the flexible flattened tube forms a resilient foundation which prevents the wire from crystallizing and the breaking of the circuit is thus prevented.

g A further advantage of the flattened folded tube 7 is that it allows for the ready soldering of the current supply leads to the two copper wires at positions within the confines and protection of the tube 7 merely by temporarily opening up the ends of said tube as Furthermore, the

illustrated. The threading or lacing of the copper wires through the various holes in the tube 7 maintains the wires in proper spaced position without undue binding and avoids short circuit of the incoming leads.

Having thus described my invention what I do claim as new and desire to secure by Letters Patent is:

1. In an electric heating device, a flexible double strip forming a flattened tube foundation, an electric resistance heating coil wound about said flattened tube with electric feeding leads extending through said flattened tube and. connected to said heating coil, and a waterproof and water indissoluble enclosure for said foundation.

2. In an electric heating device, a flexible hollow foundation having holes therein, an electric resistance heating wire coil wound about said foundation, the feeding leads to said resistance heating wire coil being threaded through said holes to keep said leads in position and whereby said leads are secured within the hollow foundation.

In testimony whereof I have signed my name to this specification.

CARL GRAF. 

